The present invention generally relates to an automotive differential. More specifically, the present invention relates to an automotive differential which can be selectively locked to prevent relative rotation of two axle half shafts.
In an automotive vehicle, a differential gear assembly is typically used to transfer power from a rotating driveshaft to the axles and wheels of the vehicle. The rotating driveshaft of the vehicle typically engages a ring gear which is mounted onto a differential housing. The end of the driveshaft and the ring gear are adapted to transfer rotation from the drive shaft to the differential housing such that the differential housing rotates transverse to the driveshaft. Within the differential housing, the ends of the axles of the vehicle are supported and connected to the differential housing through a differential gear set, such as a bevel differential gear set. Thus, the ring gear of the differential housing allows the driveshaft to rotate the differential housing in a direction transverse to the driveshaft, whereby the differential gear set rotates the axles of the vehicle to drive the wheels of the vehicle.
Typically, the differential gear set includes a pair of side gears, and a pair of pinion gears. Most commonly, the pinion gears are supported by a pinion pin which extends across the differential housing. The pinion gears are allowed to rotate on the pinion pin thereby allowing the vehicle axle shafts to rotate relative to one another.
In a limited slip differential assembly, the axle shafts are capable of being locked together such that the rear wheels of the vehicle are not allowed to rotate relative to one another. One way of doing this is to provide a clutch pack within the differential assembly which is mounted between the differential housing and one of the side gears. When an axial force is placed upon the clutch pack, the side gear will be rotationally locked to the differential housing, thereby preventing the two side gears, and thereby the two axle half-shafts from rotating relative to one another.
One way of applying an axial force onto a clutch pack of this type is with a ball ramp. A ball ramp is comprised of a pair of plates having opposing channels formed therein. Within the channels are balls. The height of the balls is such that the plates are not allowed to touch. The channels are ramped such that when one plate rotates relative to the other, the balls will roll up the ramped channels and force the plates apart, thereby producing an axial force.
Over time, the channels within the plates will wear, which means less axial movement of the plates occurs as the ball bearings roll up the ramped surfaces. This reduces the amount of axial force produced by the ball ramp, and affects the performance of the clutch. The only way to repair this condition is to reposition or replace the ball ramp. Further, a ball ramp will only move a limited distance away from the clutch pack. Therefore, the clutch pack cannot be relieved further to allow cooling.
Therefore, there is a need for a differential having a clutch pack for selectively locking one of the side gears to the differential housing having a device that applies an axial force to the clutch pack and can be tuned to accommodate for wear of the clutch pack and wear within the device, as well as allowing the device to be backed away from the clutch pack to allow the clutch pack to cool.